Studies On Determination, Preparation Of Microcystins In Environment And Its Degradation By Photocatalysis

The occurrence of toxic water bloom of cyanobacteria algae has been a serious pollution problem in recent years. Microcysins (MCs) is a group of extremely hepatotoxic toxin produced by the species of cyanobacteria. Due to complicated structure and diverse congener, the MCs pollution is characteristic of trace-level, recalcitrant and complex in eutrophic freshwater. It has been proven difficult to be removed by conventional water treatments and constitute potential hazard to public health, some necessary measures of monitoring and determination on MCs are urgently needed. Furthermore, purified MCs are also needed to utilize as reagent material in relevant research field, such as degradation of MCs in drinking water with high efficiently. Focused on determination and purification of MCs, as well as degradation by photo-Advanced Oxidation Process, this dissertation selected the water and bloom sample from Meiliang Bay, TaiHu Lake as objective to conduct a series of investigation.To optimize and develop two methods of trace level MCs determination based on solid phase extraction (SPE)-high performance liquid chromatography (HPLC) and ELISA, single factor comparisons were conducted in such key SPE processes as cartridge, rinse, elution and concentration. MCs in water sample could be condensed 1000 times by this method. When methanol solution with trifluoroacetic acid (TFA) was applied to mobile phase, HPLC assay offered a good potential for a sensitive and selective determination of MCs. The results were compared and validated between SPE-HPLC with ELISA method. According to the results for water samples from TaiHu lake during warm months, MC-RR and MC-LR were main MCs component, and the content of former was usually greater than the later. The maximum contents of both MCs which appeared in September have exceeded the guideline and some measures must be taken to make MCs pollution under control.At the room temperature, the 60% methanol solution with ultrasonic method was applied to extract MCs from bloom sample. The massive of phycocyanin protein was removed by adjusting the pH of solvents to the isoelectric point. SPE-HPLC has been employed to isolate MCs and the structures of the obtained MCs were further identified with HPLC, spectrophotometer, and electrospray ionization mass spectrometry (ESI-MS). The result showed that MC-RR, MC-LR and MC-YR were main MCs component in bloom sample, with a small quantity of Dimethyl MC-RR and a kind of unknown MCs. Methods were also established to isolate and purify MCs with Flash chromatography and preparative chromatography. Under the condition of mobile phase with 55% methanol solution, flow rate 10ml/min and injection volume 400μL, about 0.1mg pure MC-RR and MC-LR were obtained.